Hemodialysis using disposable dialyzers has become an extensively used method for the treatment of persons with kidney dysfunction or failure. Hollow fiber dialyzers having a blood compartment composed of a bundle of hollow fibers and a dialysate compartment formed by a sleeve surrounding the fiber bundle are a very widely used dialyzer of this type. While hemodialysis treatment has resulted in an improvement and in the prolongation of life, it is plagued with extremely high cost. As one method of reducing this cost, research has been performed which concluded that disposable hollow fiber dialyzers may be reused if they are adequately cleansed of bacterial, protein and other particulate matter. The cleaned dialyzer must be tested for sufficient dialyzing capability (the hollow fibers eventually become plugged) and for leakage between the blood and dialysate compartment caused by broken fibers or broken seals.
Several machines for cleaning dialyzers have been developed, one of which includes testing means for testing leakage and dialyzing capability. The dialyzing capability test involves an evaluation of the ultrafiltration capability of the cleaned dialyzer.
It has been reported that ultrafiltration is not a reliable measurement of the dialyzing capability of cleansed dialyzers. The measured ultrafiltration capability may remain high while the dialyzer loses its ability to transfer important solutes of low and middle molecular weight. Measurement of the volume of the dialyzer blood compartment ie., the internal volume of the blood compartment fiber bundle, has been shown to provide a much more reliable indicator of the dialyzing capability of a hollow fiber dialyzer than ultrafiltration measurement techniques. The fiber bundle volume is related directly to the surface area of the blood compartment--the principal factor affecting the mass transfer capability of the dialyzer. Furthermore, even with new dialyzers, the dialyzer blood compartment volume is manufactured to a closer specification than is ultrafiltration capability. To date, however, no automatic means for measuring the blood compartment volume of a cleansed dialyzer has been developed.